1. Chapter 8: Crowl & Louvar
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Chemical Reactivity
Chapter 8: Crowl & Louvar

2. Chemical Reactive Hazard
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Chemical Reactive Hazard
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Chemical reactivity hazard: situation with potential for an uncontrolled chemical reaction, resulting in harm to people, equipment, or environment.
Result could be:
Violent release of heat, toxic or flammable materials
Build up of excessive pressure
Reaction could be:
Self-reacting chemical (i.e., monomer)
With other chemicals; intentional or otherwise
Catalyzed by contamination, construction materials
Exothermic and/or gas producing
Due to incompatibility

3. Screening for Reactive Hazards
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Screening for Reactive Hazards
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Figure 8-1 Screening flowchart for reactive chemical hazards. An answer of “yes” at any decision point moves more toward reactive chemisty. See Section 8.2 for more details. (Source: R.W Johnson, S.W. Rudy, and S. D. Unwin, Essential Practices for Managing Chemical Reactivity Hazards (New York: AIChE Center for Chemical Process Safety, 2003.))

4. Specific Chemical Reactive Hazard
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Specific Chemical Reactive Hazard
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5. Specific Chemical Reactive Hazard
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Specific Chemical Reactive Hazard
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6. Specific Chemical Reactive Hazard
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Specific Chemical Reactive Hazard
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7. Specific Chemical Reactive Hazard
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Specific Chemical Reactive Hazard
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Table AF-1: A few pyrophoric and spontaneously combustible categories and chemicals (these materials combust on exposure to air).
Table AF-2: Some chemical structures susceptible to peroxide formation (the peroxides formed may become unstable and explode when disturbed).
Table AF-3: Chemical categories susceptible to water reactivity.
Table AF-4: Common water-reactive chemicals.
Table AF-5: Typical oxidizers.
Table AF-6: Some polymerizing compounds (these chemicals may polymerize rapidly with release of large amounts of heat).

8. Reactive Functional Groups
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Reactive Functional Groups
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9. Sources of Information
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Sources of Information
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10. Understanding Reactive Systems
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Understanding Reactive Systems
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Cooling Water
Exothermic Reaction
Runaway reactions can occur whenever exothermic chemistry is used.
Why important: Common problem with exothermic reactions.

11. Understanding Reactive Systems
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Understanding Reactive Systems
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12. Runaway Reactions How? 1. Loss of coolant. 2. Increased temperature.
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Runaway Reactions
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How?
1. Loss of coolant.
2. Increased temperature.
3. Increased energy generation.
High pressure due to: Vapor pressure of liquid.
Vapor decomposition products.
Larger vessels respond faster - less heat transfer thru walls!!!
Some chemicals can achieve self heat rates of 100’s deg. C/min! Styrene, Acrylic Acid
There are lots of ways for runaway reactions to occur. People somehow do not realize that a larger vessel will runaway faster since it has a lower surface to volume ratio with less heat losses.

13. Runaway Reactions Some ways for runaways to occur: Loss of cooling.
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Runaway Reactions
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Some ways for runaways to occur:
Loss of cooling.
Overcharge reactant.
External fire.
Mis-charge reactant.
Low reaction temperature in semi-batch reactor. This is called a sleeping reactor.
Loss of agitation.
Some ways for this to occur. Two phase flow is a very challenging engineering problem.
Most reactive runaways result in 2-phase flow thru relief and require a relief area 2 to 10 times larger than single phase relief.

14. Understanding Reactive Systems
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Understanding Reactive Systems
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15. Application of Calorimeter Data
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Application of Calorimeter Data
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Heat exchanger duty to achieve required reactor cooling
Cooling water requirements and cooling water pump size
Condenser size in a reactor reflux system
Max conc. Of reactants to prevent overpressure in the reactor
Reactor vessel size and pressure rating
Type of reactor (batch, semi-batch, tubular)
Reactor temperature control and sequencing
Semi-batch reactor reactant feed rates
Catalyst concentrations; max fill for batch and semi-batch reactors
Alarm/shutdown setpoints
Operating and emergency procedures
Relief sizing and effluent treatment systems
Solvent concentrations required to control reactor temperature
Page 415 C&L 3rd ed.

16. Improving Reactive Safety
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Improving Reactive Safety
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17. 4/12/2017
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18. Improving Reactive Safety
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Improving Reactive Safety
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19. CBE 465
In-Class Exercise
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A company had a spray painting operation to paint automotive parts. The spray painting was done in a paint booth to reduce worker’s exposure and to collect any paint droplets that might be entrained in the exhaust air. The paint droplets were collected by fibrous filters. At the end of each day, the filters were removed, placed in plastic bags, and stored for disposal in a separate building.
Due to environmental concerns over volatile emissions from paint solvents, the paint supplier reformulated the paint to use a less volatile solvent. This change was done in consultation with the paint company. Several test were done to ensure the reformulated paint worked well with the existing spray equipment and that the quality was satisfactory.
The company switched to the reformulated paint. Several days later the disposal building caught on fire, apparently due to a fire started by the paint filters. Can you explain how this might have happened. Any suggestions for prevention?

20. CBE 465
In-Class Exercise
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A university lab expansion includes installation of a distribution system to provide gaseous oxygen from manifolded cylinders to a biochemical engineering laboratory. No chemical reactivity hazards have been previously identified for the lab facilities.
Apply the screening method of Figure 8-1 to determine if any chemical reactivity hazards are expected.

21. Runaway Reactions - 4 CBE 465 4/12/2017
A picture from the 1940s showing a relief discharge thru the roof of a building.